So you will need to pay 360$ instead of 320$. Many people would choose cheaper memory. I guess, almost everyone except some PC enthusiasts (last time I discussed it, the majority of PC enthusiasts thought that ECC on desktop is not needed, so they wouldn't want to pay for it). I agree that ECC is nice to have, but price is real.
RAM prices already vary by more than 12%, and it seems like there is no shortage of people paying premium for brand recognition, different board colors (green is "out"), useless heat sinks etc. I think there would be plenty of people willing to pay extra for ECC (some for peace of mind, some because they need it, some just to feel superior)
The market segment of "people who are willing to pay a premium for computing devices" is pretty vast, isn't it?
Most people would be fine with a $200 Chromebook, $500 bare-bones Windows notebook, or a garden-variety PC from 2007 but millions of us choose to pay more because we value the additional things that newer, more powerful computing devices give us.
Lots of professionals and enthusiasts gladly pay large premiums for higher-spec gear, even when the improvements are quite small, because those small improvements are enjoyed over many thousands of hours of lifetime use.
Perhaps more to the point, you already see gamers paying premiums for higher-specced memory to enable their overclocking and tweaking endeavors.
So I definitely think there's a market of people who'd pay more for ECC...
I guess they will pay for higher frequency, but for ECC? Not so much. It won't help to achieve higher geek rating after all. I might be totally wrong about it, of course.
Just like I paid extra for a nice PSU instead of the very cheapest, I would pay more for ECC.
The cost difference for ECC amortized over the life of the hardware is negligible compared to the annoyance and time spent trying to work out what's causing those random bluescreens/reboots/corruption.
That's actually a price I would be willing to pay.